1. Field of the Invention
The present invention relates to a method for analyzing a film structure and an apparatus therefor. More particularly, the invention relates to a method for analyzing a film structure for interface roughness and pore distribution of a single layer film or a multi-layer film, and an apparatus therefor.
2. Description of the Related Art
As a method for analyzing the surface and interface of a thin film specimen, a microscope technique using, for example, an electron microscope, is generally employed, and a large amount of information can be obtained with this real-space observation. However, it in fact involves such problems as restriction in observable areas, damage to the specimen, and difficulty in analyzing an interface inside the film.
As nondestructive inspection methods for analyzing a film structure, X-ray reflectivity measurement and X-ray diffuse scattering measurement have been employed.
A method for analyzing a particle diameter distribution of a specimen having an uneven density, such as a porous film, by utilizing X-ray reflectivity measurement has been proposed by the inventor of the present invention (as described in JP-A-2001-349849). In the analyzing method, a diffuse scattering intensity of an X-ray is measured, and a particle diameter distribution is analyzed based on the measured values.
Upon emitting an X-ray at an angle to graze a surface of a thin film, the incident X-ray is reflected and transmitted. At this time, the grazing incident angle is in the vicinity of the total reflection critical angle of the film, and the (penetrating) X-ray can hardly at all penetrate into the interior of the thin film due to the effect of refraction, but proceeds as an evanescent wave beneath the surface of the thin film in a region of several nanometers below the surface. Accordingly, analysis of the surface structure of a thin film is enabled in the case where an X-ray is made grazing incident with an incident condition close to the total reflection critical angle.
A surface or interface of a thin film has an electron density fluctuation (roughness) on the order of several nanometers in the direction normal to the surface of the specimen. Such a method for analyzing a specimen having an uneven density and an apparatus and system therefor have been proposed (in JP-A-2003-14663) that an X-ray transmitted almost parallel to the surface of the specimen creates an X-ray profile corresponding to the shape of the surface or interface of the specimen, the profile then being analyzed to determine the surface or interface shape.
Although excellent analyzing capabilities are realized by the methods for analyzing a specimen having an uneven density using X-rays proposed by the inventors and others, these methods cannot analyze the shape of the interface and the pore size of the specimen simultaneously. Furthermore, they assume that the target of analysis is a single layer film and are difficult to apply to a specimen having a multi-layer structure. Furthermore, in the case where the absolute amount of the particles or pores in the thin film is small. (i.e., the density of the particles or pores per unit volume is small), X-ray scattering due to the roughness of the surface or interface becomes pronounced relative to the scattering due to particles or pores. There is such a problem that the scattering due to surface or interface roughness is due only to the electron densities at the surface, and does not depend on the film thickness.